Sudanese rebels say they have launched a major operation against an area in South Kordofan which a controversial counter-insurgency unit showed off to journalists after "liberating" it last week.
The United States on Thursday urged Sudan to safeguard the right of peaceful assembly, after security forces allegedly shot and killed a university student.
Sudanese police allegedly opened fire Monday on demonstrators from a camp for displaced people in the troubled Darfur region, wounding an unconfirmed number, peacekeepers said.
The United States and other foreign powers stepped up pressure on South Sudan's feuding ethnic factions to settle their differences, as Washington dispatched an envoy to the violence-wracked region.